The present invention relates to an evaporated fuel treatment device. The evaporated fuel treatment device is provided in a system for supplying fuel from a fuel tank to an engine, and functions to detect failure, for example, of a pressure sensor that detects an inner pressure of the fuel tank.
Japanese Laid-Open Patent Publication H08-74678 discloses an evaporated fuel treatment device that causes evaporated fuel in a fuel tank to be sucked in by an engine. The evaporated fuel treatment device includes a device for detecting a failure of a pressure sensor that detects an inner pressure of the fuel tank. The failure detecting device has a switching valve for switching between a state in which the pressure sensor is connected to the fuel tank and a state in which atmospheric pressure is supplied to the pressure sensor. When the detection value of the pressure sensor is beyond a predetermined range including the atmospheric pressure, the failure detecting device is switched from the state in which it is connected to the fuel tank to the state in which the atmospheric pressure is supplied thereto. At this time, when the pressure sensor does not detect the atmospheric pressure, it is determined that the pressure sensor is out of order. Thus, the conventional evaporated fuel treatment device, which requires a switching valve, is of a relatively complicated structure.